Nonadherence to medications is common among patients with diabetes and contributes to suboptimal control of glycemic and lipid plasma levels. Adherence is not routinely measured in clinical practice because no valid, feasible methods have been readily available. The lack of medication adherence information contributes to clinician failure to identify and address patient nonadherence and to clinical inertia and poor health outcomes. Existing electronic prescribing systems hold the potential to display medication adherence information. We propose a 2-arm cluster-randomized trial to test the effectiveness of providing PCPs with both adherence measurements and an adherence clinic to improve adherence to diabetic and lipid-lowering drugs. This adherence clinic will consist of a pharmacist and nurse trained in motivational interviewing (Ml) techniques to improve adherence to medications. Adherence indices will be generated by linking e-prescribing information with pharmacy data. The trial will be conducted among 1,436 patients with diabetes and poor blood glycemic and/or lipid control. Primary care providers will be randomized to 1 of the following 2 study arms: 1) usual care--PCPs will write prescriptions electronically but will not be provided patient adherence information or Ml support;and 2) intervention--PCPs will be provided adherence information and adherence prompts electronically plus physicians and patients will receive support from an adherence clinic. Our intervention uses as theoretical behavioral framework elements of the Chronic Care Model, Self-Determination Theory, and the Health Belief Model. The study will use qualitative methods to guide intervention design and implementation and will include both process evaluation and treatment fidelity measures. The intervention will be tailored to patients'adherence and goal levels. Outcomes will include adherence to diabetes and lipid-lowering medications;cholesterol and glycated hemoglobin plasma levels (primary outcome);patients and providers'acceptance and satisfaction;and cardiovascular morbidity- mortality (exploratory outcome). The study will also evaluate the cost effectiveness of the intervention. Patients will be followed for 36 months. Analyses will control for cluster randomization effects. The introduction of sustainable medication adherence monitoring in clinical practice holds great potential to improve health outcomes among patients with diabetes.